deploying a fully routed enterprise campus network€¦ · • eigrp/ospf routing preference over...

1© 2005 Cisco Systems, Inc. All rights reserved.RST-203111207_05_2005_c2

DEPLOYING A FULLY ROUTED ENTERPRISE CAMPUS NETWORKSESSION RST-2031


Agenda

• Campus Network Designs

• Routed Access Design

• EIGRP Design Details

• OSPF Design Details

• PIM Design Details

• Summary


Hierarchical Campus DesignBuilding Blocks

Data CenterWAN Internet

SiSi SiSi SiSi SiSi SiSi SiSi

SiSi SiSi

SiSi SiSiSiSi SiSi

SiSi SiSi

Access

Distribution

Core

Distribution

Access • Offers hierarchy—each layer hasspecific role

• Modular topology—building blocks• Easy to grow, understand, and

troubleshoot• Creates small fault domains—clear

demarcations and isolation• Promotes load balancing and

redundancy• Promotes deterministic traffic patterns• Incorporates balance of both Layer 2 and

Layer 3 technology, leveraging the strength of both

• Can be applied to all campus designs; multilayer L2/L3 and routed access designs


Tried and True: Reference DesignMultilayer L2/L3 Design

• Consider fully utilizing uplinks via GLBP• Distribution-to-distribution link required for route summarization• No STP convergence required for uplink failure/recovery• Map L2 VLAN number to L3 subnet for ease of use/management• Can easily extend VLANs across access layer switches if required

10.1.20.010.1.120.0

VLAN 20 DataVLAN 120 Voice


10.1.40.010.1.140.0

HSRP or GLBPVLANs 20,120,40,140

HSRP or GLBPVLANs 20,120,40,140

ReferenceModel

Layer 3SiSiSiSi

Layer 2

Access

Distribution


Data Center

SiSi SiSi

SiSi SiSi

SiSi SiSi

Hierarchical Campus DesignMultilayer L2/L3 Building Blocks

• Highly available and fast—always on• Deploy QoS end-to-end: protect the good and

punish the bad • Equal cost core links provide for best

convergence • Optimize CEF for best utilization of redundant

L3 paths

• Aggregation and policy enforcement• Use HSRP or GLBP for default gateway protection• Use Rapid PVST+ if you MUST have L2 loops in

your topology• Keep your redundancy simple; deterministic

behavior = understanding failure scenarios and why each link is needed

• Network trust boundary• Use Rapid PVST+ on L2 ports to prevent loops in

the topology• Use UDLD to protect against 1 way interface UP

connections• Avoid daisy chaining access switches • Avoid asymmetric routing and unicast flooding,

don’t span VLANS across the access layer

Access

Distribution

Core

Distribution

Access


Routing to the Edge Layer 3 Distribution with Layer 3 Access

• Move the Layer 2/3 demarcation to the network edge

• Upstream convergence times triggered by hardware detection of link lost from upstream neighbor

• Beneficial for the right environment

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10.1.40.010.1.140.0

EIGRP/OSPF EIGRP/OSPF

GLBP Model

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Layer 3

Layer 2

Layer 3

Layer 2EIGRP/OSPF EIGRP/OSPF


Data Center

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Hierarchical Campus DesignRouted Access Building Blocks

• Highly available and fast—always on• Deploy QoS end-to-end: protect the good and

punish the bad • Equal cost core links provide for best

convergence

• Access layer aggregation • Route summarization to the core to minimize

routing events• Route filtering from the core to minimize routing

table size in access• OSPF stub area border (ABR)• Keep your redundancy simple; equal cost load

balancing between access and core• Vary CEF algorithm to prevent polarization

• Network trust boundary• VLANs are contained to the access switch • Use EIGRP or OSPF on interfaces to

distribution layer• Use parallel paths for Equal Cost Multi Path

(ECMP) routing • Use EIGRP stub routers or OSPF stub areas to

limit scope of convergence events

Access

Distribution

Core

Distribution

Access


What Is High Availability?

DPM—Defects per Million

Availability Downtime Per Year (24x365)

99.000%

99.500%

99.900%

99.950%

99.990%

99.999%

99.9999%

3 Days

1 Day

53 Minutes

5 Minutes

30 Seconds

15 Hours

19 Hours

8 Hours

4 Hours

36 Minutes

48 Minutes

46 Minutes

23 Minutes

DPM

10000

5000

1000

500

100

10

1

“High Availability”


What If You Could…Reduce Cost Through Diminished Risk of Downtime

• Costs for downtime are highOne day cost of lost productivity = $1,644 per employee

100 person office = $164K per day

• More than just a datanetwork outage

• More than just revenue impacted

Revenue loss

Productivity loss

Impaired financial performance

Damaged reputation

Recovery expenses Source: Meta Group999

$ 205$1,010,536Average

$ 107$ 668,586Transportation

$ 244$1,107,274Retail

$ 370$1,202,444Insurance

$1,079$1,495,134Financial Institution

$ 134$1,610,654Manufacturing

$ 186$2,066,245Telecommunications

$ 569$2,817,846Energy

Revenue/ Employee-

HourRevenue/HourIndustry Sector


Campus High AvailabilitySub-Second Convergence

Worst Case Convergence for Any Campus Failure Even

Sec

on

ds

00.20.40.60.8

11.21.41.61.8

2

L2 AccessOSPF Core*

L2 AccessEIGRP Core

OSPFAccess*

EIGRPAccess

L2 Access (Rapid PVST+ HSRP)

L3 Access

*OSPF Results Require Sub-Second Timers


High-Availability Networking in the Campus

Reinforced Network Infrastructure:Infrastructure Security HardeningDevice-Level and Software Resiliency

Real World Network Design:Hierarchical Network Design—Structured Modular Foundation

Network Operations:Best Practices

Real-Time Network Management:Best Practices

Best-in-Class Support:TAC, CA, Etc.


Routed Access DesignStructured Design Foundation

• EIGRP or OSPF routed links between access and distribution• Routed interfaces, not VLAN trunks, between switches• Equal cost multi path to load balance traffic across network• Route summarization at distribution (like L2/L3)• Single (IGP) control plane to configure/manage (no STP, HSRP,)

10.1.20.010.1.120.0



10.1.40.010.1.140.0

EIGRP or OSPFEqual Cost Multi Path

Layer 2

Layer 3

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SiSiSiSi Access

Distribution


Agenda






• Summary


Why Routed Access Campus Design?

• Most Catalysts® support L3 switching today• EIGRP/OSPF routing preference over spanning tree• Single control plane and well known tool set

Traceroute, show ip route, sho ip eigrp neighbor, etc…

• IGP enhancements; stub router/area, fast reroute, etc..• It is another design option available to you

Layer 2

Layer 3

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SiSiSiSi Access

Distribution


Ease of Implementation

• Less to get right:No STP feature placement coreto distribution

LoopGuardRootGuardSTP Root

No default gateway redundancy setup/tuning

No matching of STP/HSRP/GLBP priority

No L2/L3 multicast topology inconsistencies


Ease of Troubleshooting

• Routing troubleshooting toolsShow ip route

Traceroute

Ping and extended pings

Extensive protocol debugs

Consistent troubleshooting; access, dist, core

• Bridging troubleshooting toolsShow ARP

Show spanning-tree, standby, etc…

Multiple show CAM dynamic’s to find a host

• Failure differencesRouted topologies fail closed—i.e. neighbor loss

Layer 2 topologies fail open—i.e. broadcast and unknowns flooded


Routing to the Edge Advantages? Yes, in the Right Environment

• EIGRP and OSPF converge in


Routed Access Considerations

• Do you have any Layer 2 VLAN adjacencyrequirements between access switches?

• IP addressing—do you have enough addressspace and the allocation plan to support arouted access design?

• Platform requirements;Catalyst 6500 requires an MSFC with hybrid (CatOS and Cisco IOS®) in the access to get all the necessary switchport and routing features

Catalyst 4500 requires a SUP4 or higher for EIGRP or OSPF

Catalyst 3500s and 3700s require an enhanced Cisco IOS image forEIGRP and OSPF


Interior Gateway Protocol OptionsStatic Routing

• BenefitsPrice; in default Cisco IOS feature set for routers and Layer 3 switches

• ConsiderationsConfiguration intensive and prone to error

Potential routing black holes during some failure conditions

• Design guidanceDefault route from the access to the distribution

Specific route from the distribution to the access

Set next-hop to neighbor’s adjacent IP interface address to minimize black holes during failure conditions

Redistribute static routes from distribution to core—summarize access subnets when possible


Interior Gateway Protocol OptionsRIP Routing

• BenefitsWidely supported

Price; in default Cisco IOS feature set of Catalyst L3 switches

• ConsiderationsSlow convergence time

Limited network diameter; max hops = 16

Redistributing into an advanced IGP?

• Design guidanceUse RIP version two; VLSM

Tune hellos down to one second

Summarize routes from distribution to core

Use routed interfaces vs. VLAN trunks


Interior Gateway Protocol OptionsEIGRP Routing

• BenefitsSimple to configure

Extremely fast convergence without tuning

Scales to large topologies

Flexible topology options

• ConsiderationsCisco innovation

Summarization to limit query range

Price; requires enhanced IOS image in some Catalysts

• Design guidanceLater in the presentation


Interior Gateway Protocol OptionsOSPF Routing

• BenefitsFast convergence with tuning

Widely deployed industry standard

• ConsiderationsDesign and configuration complexity

Price; requires enhanced IOS image in most Catalysts

Topology design restrictions

• Design guidanceLater in the presentation


EIGRP vs. OSPF as Your Campus IGPDUAL vs. Dijkstra

• Convergence:Within the campus environment, both EIGRP and OSPF provide extremely fast convergence

EIGRP requires summarization

OSPF requires summarization and timer tuning for fast convergence

• Flexibility:EIGRP supports multiple levels of route summarization and route filtering which simplifies migration from the traditional multilayer L2/L3 campus design

OSPF area design restrictions need to be considered

• Scalability:Both protocols can scale to support very large enterprise network topologies

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OSPF OPSF 12.2S EIGRP

UpstreamDownstream


CEF Load BalancingAvoid Underutilizing Redundant Layer 3 Paths

• The default CEF hash‘input’ is L3

• CEF polarization: In a multi-hop design, CEF could select the same left/left or right/right path

• Imbalance/overload could occur

• Redundant paths are ignored/underutilized

Redundant PathsIgnored

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L

L

R

RDistribution

Default L3 Hash

CoreDefault L3 Hash

DistributionDefault L3 Hash

AccessDefault L3 Hash



CEF Load BalancingAvoid Underutilizing Redundant Layer 3 Paths

• With defaults, CEF could select the same left/left or right/right paths and ignore some redundant paths

• Alternating L3/L4 hash and default L3 hash will give us the best load balancing results

• The default is L3 hash—no modification required in core or access

• In the distribution switches use:

mls ip cef load-sharing full

to achieve better redundant path utilization

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RL

RDistributionL3/L4 Hash

CoreDefault L3 Hash

DistributionL3/L4 Hash

L

RL

Left Side Shown



L

All PathsUsed

Note: Catalyst 6500 SUP720 does not require CEF tuning


Routed Access DesignHigh-Speed Campus Convergence

• Convergence is the time needed for traffic to be rerouted to the alternative path after the network event

• Network convergence requires all affected routers to process the event and update the appropriate data structures used for forwarding

• Network convergence is the time required to:

Detect the event

Propagate the event

Process the event

Update the routing table/FIB

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High-Speed Campus Convergence—Event Detection

• When physical interface changes state, the routing process is notified

This should happen in the ms range

• Some events are detected by therouting protocol

L2 switch between L3 devices is a typical example

Neighbor is lost, but interface is UP/UP

Hello mechanism has to detect the neighborloss

• To improve failure detectionUse routed interfaces between L3 switches

Decrease interface carrier-delay to 0s

Decrease IGP hello timersEIGRP: Hellos = 1, Hold-down = 3OSPF: Hellos = 250ms

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SiSi

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Hello’s

L2 Switch orVLAN Interface

RoutedInterface


High-Speed Campus Convergence—Propagate the Event

• When an event occurs that changes the topology, all routers that were previously aware of the path need to be notified about the topology change

• EIGRP uses the query/reply process to find alternate paths

• OSPF propagates LSAs and all affected routers recalculate SPF to find alternate paths

LSA timer tuning can improve OSPF event propagation performance

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SummaryRouteFilter

• Summarization and route filtering can be used to limit the number of routers needing to participate in a network topology change event


High-Speed Campus Convergence—Process the Event

• Once a router has been notified that a topology changing event has occurred, it must recalculate a new path or topology for forwarding traffic

• EIGRP uses the DUAL algorithm to calculate a next hop successor(s) and possibly feasible successor(s)

• OSPF uses the Dijkstra SPF algorithm to calculate a shortest path tree for the new topology

SPF timer tuning can speed up SPF processing time


High-Speed Campus Convergence—Update the Routing Table and FIB

• After a new path or topology has been calculated by the protocol algorithm, the routing table must be updated

Routing Information Base (RIB) is the routing table

Forwarding Information Base (FIB) is based on the RIB and used by the hardware to forward traffic

• Projects are under way to make the RIB faster, more scalable and to improve the FIB info download to the line-cards

A B

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Traffic Dropped Until

LSA Generated/

Processed and

Routing Table/FIB

Updated

• Summarization and route filtering can be used to limit the number of routes needed in the RIB and FIB


Agenda






• Summary


Strengths of EIGRP

• Advanced distance vector

• Maps easily to the traditional multilayer design

• 100% loop free

• Fast convergence

• Easy configuration

• Incremental update

• Supports VLSM and discontiguous network

• Classless routing

• Protocol independentIPv6, IPX and AppleTalk

• Unequal cost paths load balancing

• Flexible topology design options


EIGRP Design Rules for HA CampusSimilar to WAN Design, But…

• EIGRP design for the campus follows all the same best practices as you use in the WAN with a few differences

No BW limitations

Lower neighbor counts

Direct fiber interconnects

Lower cost redundancy

HW switching

• WAN à stability and speed

• Campus à stability, redundancy, load sharing, and high speed

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EIGRP in the CampusConversion to an EIGRP Routed Edge

• The greatest advantages of extending EIGRP to the access are gained when the network has a structured addressing plan that allows for use of summarization and stub routers

• EIGRP provides the ability to implement multiple tiers of summarization and route filtering

• Relatively painless to migrateto a L3 access with EIGRP if network addressingscheme permits

• Able to maintain a deterministic convergence time in very large L3 topology

10.10.0.0/1710.10.128.0/17

10.10.0.0/16

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EIGRP Protocol Fundamentals

Metric:• Metric = [K1 x BW + (K2 x BW)/(256 - Load) +

K3 x Delay] x [K5/(Reliability + K4)] x 256By Default: K1 = 1, K2 = 0, K3 = 1, K4 = K5 = 0

• Delay is sum of all the delays along the pathDelay = Delay/10

• Bandwidth is the lowest bandwidth link along the pathBandwidth = 10000000/Bandwidth

Packets:• Hello: establish neighbor relationships

• Update: send routing updates

• Query: ask neighbors about routing information

• Reply: response to query about routing information

• Ack: acknowledgement of a reliable packet


EIGRP Protocol Fundamentals (Cont.)

DUAL Algorithm• Diffusing update algorithm

• Finite-state-machineTrack all routes advertised by neighbors

Select loop-free path using a successor and remember any feasible successors

If successor lostUse feasible successor

If no feasible successorQuery neighbors and recompute new successor

• A successor is a neighbor that has met the Feasibility Condition(FC) and has the least cost path towards the destination

• Multiple successors are possible (load balancing)

• A feasible successor is the neighbor with the next best loop free next hop towards destination


EIGRP Design Rules for HA CampusLimit Query Range to Maximize Performance

• EIGRP convergence islargely dependent on query response times

• Minimize the number of queries to speed up convergence

• Summarize distribution block routes upstream to the core

Upstream queries are returned immediately with infinite cost

• Configure all access switches as EIGRP stub routers

No downstream queries areever sent

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EIGRP NeighborsEvent Detection

• EIGRP neighbor relationships are created when a link comes up and routing adjacency is established

• When physical interface changes state, the routing process is notified

Carrier-delay should be set as a rule becauseit varies based upon the platform

• Some events are detected by therouting protocol

Neighbor is lost, but interface is UP/UP

• To improve failure detectionUse Routed Interfaces and not SVIsDecrease interface carrier-delay to 0Decrease EIGRP hello andhold-down timers

Hello = 1Hold-down = 3

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interface GigabitEthernet3/2ip address 10.120.0.50 255.255.255.252ip hello-interval eigrp 100 1ip hold-time eigrp 100 3carrier-delay msec 0

Hello’s

RoutedInterface

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L2 Switchor VLAN Interface


EIGRP Query ProcessQueries Propagate the Event

• EIGRP is an advanced distant vector; it relies on its neighbor to provide routing information

• If a route is lost and no feasible successor is available, EIGRPactively queries its neighbors for the lost route(s)

• The router will have to get replies back from ALL queried neighbors before the router calculatessuccessor information

• If any neighbor failsto reply, the queried routeis stuck in active and therouter resets the neighborthat fails to reply

• The fewer routers and routesqueried, the faster EIGRP converges; solution is to limit query range

SiSiSiSi

Query

SiSiSiSi

SiSiSiSi

Query

Query

Query

Query

Query

Query

Query

Query

Reply

Reply

Reply

Reply

Reply

Reply

Reply

Reply

Reply

Traffic

Drop

ped U

ntil

EIGRP

Conv

erges

Access

Distribution

Core

Distribution

Access


A CB 130.130.1.0/24

B Summarizes 130.0.0.0/8 to A

130.x.x.x

Reply with Infinity and theQuery Stops Here!

Query for130.130.1.0/24

EIGRP Query Range

• Summarization pointAuto or manual summarization bound queries

Requires a good address allocation scheme

• Stubs also help to reduce the query range

X129.x.x.x

Query for130.130.1.0/24

8


EIGRP SummarizationSmaller Routing Tables, Smaller Updates, Query Boundary

• Auto summarization:On major network boundaries, networks are summarized to themajor networksAuto summarization is turned on by default

• Manual summarizationConfigurable on per interface basis in any router within networkWhen summarization is configured on an interface, the router immediately creates a route pointing to null zero with administrative distance of five (5)

Loop prevention mechanismWhen the last specific route of the summary goes away, the summaryis deletedThe minimum metric of the specific routes is used as the metric of the summary route

192.168.1.x

192.168.1.0

192.168.2.x


10.130.0.0/16

Manual EIGRP Summarization

10.130.1.0/24

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10.130.2.0/24 10.130.3.0/24 10.130.254.0/24

ip summary-address EIGRP

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interface gigabitethernet 3/1ip address 10.120.10.1 255.255.255.252ip summary-address eigrp 1 10.130.0.0 255.255.0.0


No Queries to Rest of Network

from Core

EIGRP Query Process with Summarization

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Query Query

Query ReplyReply

Reply

Reply8Reply8

interface gigabitethernet 3/1ip address 10.120.10.1 255.255.255.252ip summary-address eigrp 1 10.130.0.0 255.255.0.0

SummaryRoute

SummaryRoute

Traffic

Drop

ped U

ntil

EIGRP

Conv

erges

• When we summarize from distribution to core for the subnets in the access we can limit the upstream query/reply process

• In a large network this could be significant because queries will now stop at the core; no additional distribution blocks will be involved in the convergence event

• The access layer is still queried


EIGRP Stubs

• A stub router signals (through the hello protocol) that it is a stub and should not transit traffic

• Queries that would have been generated towards the stub routers are marked as if a “No path this direction” reply had been received

• D1 will know that stubs cannot be transit paths, so they will not have any path to 10.130.1.0/24

• D1 simply will not query the stubs, reducing the total number of queries in this example to 1

• These stubs will not pass D1’s advertisement of 10.130.1.0/24 to D2

• D2 will only have one path to 10.130.1.0/24

D2D1

Distribution

Access

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10.130.1.0/24

Hello, I’m a Stub…

I’m Not Going to Send You Any Queries Since You Said That!


EIGRP Stubs

• Connected: advertise directly connected networks

• Static: advertise redistributed static routes

• Summary: advertise locally created summaries

• Receive-only: don’t advertise anything

router(config-router)#EIGRP stub ?connected Do advertise connected routesreceive-only Set IP-EIGRP as receive only neighborstatic Do advertise static routessummary Do advertise summary routes


No Queries to Rest of Network

from Core

EIGRP Query ProcessWith Summarization and Stub Routers

• When we summarize from distribution to core for the subnets in the access we can limit the upstream query/reply process

• In a large network this could be significant because queries will now stop at the core; no additional distribution blocks will be involved in the convergence event

• When the access switches are EIGRP stub’s we can furtherreduce the query diameter

• Non-stub routers do not query stub routers—so no queries will be sent to the access nodes

• No secondary queries—and only three nodes involved in convergence event

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Query Reply

Reply8Reply8

Stub Stub

SummaryRoute

SummaryRoute

Traffic

Drop

ped U

ntil

EIGRP

Conv

erges


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EIGRP Route Filtering in the CampusControl Route Advertisements

• Bandwidth is not a constraining factor in the campus but it is still advisable to control number of routing updates advertised

• Remove/filter routes from the core to the access and inject a default route with distribute-lists

• Smaller routing table in access is simpler to troubleshoot

• Deterministic topologyrouter eigrp 100network 10.0.0.0distribute-list Default out

ip access-list standard Defaultpermit 0.0.0.0


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EIGRP Routed Access Campus DesignOverview

• Detect the event:Set hello-interval = 1 second and hold-time = 3 seconds to detect soft neighbor failures

Set carrier-delay = 0

• Propagate the event:Configure all access layer switches as stub routers to limit queries from the distribution layer

Summarize the access routes from the distribution to the core to limit queries across the campus

• Process the event:Summarize and filter routes to minimize calculating new successors for the RIB and FIB

SummaryRoute

Stub

For More Discussion on EIGRPDesign Best Practices—RST-3220-3222


Agenda






• Summary


Open Shortest Path First (OSPF) Overview

• OSPFv2 established in 1991 with RFC 1247

• Goal—a link state protocol more efficient and scaleable than RIP

• Dijkstra Shortest Path First (SPF) algorithm

• Metric—path cost

• Fast convergence

• Support for CIDR, VLSM, authentication, multipathand IP unnumbered

• Low steady state bandwidth requirement

• OSPFv3 for IPv6 support


OSPF MetricCost = Metric

• Cost applied on all router link paths

• The lower the more desirable

• Route decisions made on total cost of path

• Derived from bandwidth100000000 ÷ bandwidth 56-kbps serial link = 1785

Ethernet = 10 64-kbps serial link = 1562

T1 (1.544-Mbps serial link) = 65 Fast Ethernet = 1

• Configured via:Interface subcommand: bandwidth

Interface subcommand: ip ospf cost

Router subcommand: ospf auto-cost reference bandwidth


Hierarchical Campus DesignOSPF Area’s with Router Types

Data CenterWAN InternetBGP


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Area 0

Area 200

Area 20 Area 30Area 10

BackboneBackbone

ABR’s ABR’s

Internal’sInternal’s

Area 0

ABR’s

Area 100

ASBR’s

ABR’s

ABR’sArea 300

Access

Distribution

Core

Distribution

Access


OPSF Design Rules for HA CampusWhere Are the Areas?

• Area size/border is bounded by the same concerns in the campus as the WAN

• In campus the lower number of nodes and stability of local links could allow you to build larger areas however…

• Area design also based on address summarization

• Area boundaries should define buffers between fault domains

• Keep area 0 for core infrastructure do not extend to the access routers

Data CenterWAN Internet


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Area 100 Area 110 Area 120

Area 0


OSPF in the CampusConversion to an OSPF Routed Edge

• OSPF designs that utilize an area for each campus distribution building block allow for straight forward migration to Layer 3 access

• Converting L2 switches to L3 within a contiguous area is reasonable to consider as long as new area size is reasonable

• How big can the area be?

• It depends!Switch type(s)

Number of links

Stability of fiber plant

Area 200Branches

Area 0Core

Area 10Dist 1

Area 20Dist 2

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OSPF in the CampusConversion to an OSPF Routed Edge

• Other OSPF area designs may not permit an easy migration to a layer 3access design

• Introduction of another network tier via BGP maybe required

• Extension of area’s beyond good design boundaries will result in loss of overall availability

External Network

Area 0Backbone

Area 100Non-Stub

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RedistributingExternals


When a Link Changes State

• Every router in area hears a specific link LSA

• Each router computes shortest path routing table

Router 2, Area 1

Old Routing Table New Routing Table

Link State Table

LSA

Dijkstra Algorithm

ACK

Router 1, Area 1

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Different Types of LSAs

• Router link (LSA type 1)

• Network link (LSA type 2)

• Network summary (LSA type 3)

• ASBR (LSA type 4)

• External (LSA type 5)

• NSSA external (LSA type 7)


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Backbone Area 0

Area 120

Area Border Router

Regular AreaABRs Forward All LSAs from Backbone

An ABR Forwards the Following into an Area

Summary LSAs (Type 3)ASBR Summary (Type 4)Specific Externals (Type 5)

Access Config:router ospf 100network 10.120.0.0 0.0.255.255 area 120

Distribution Configrouter ospf 100summary-address 10.120.0.0 255.255.0.0network 10.120.0.0 0.0.255.255 area 120network 10.122.0.0 0.0.255.255 area 0

External Routes/LSA Present in Area 120

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Backbone Area 0

Area 120

Area Border Router

Stub AreaConsolidates Specific External Links—Default 0.0.0.0

Stub Area ABR ForwardsSummary LSAsSummary Default to ABR

Access Config:router ospf 100area 120 stubnetwork 10.120.0.0 0.0.255.255 area 120

Distribution Configrouter ospf 100area 120 stub summary-address 10.120.0.0 255.255.0.0network 10.120.0.0 0.0.255.255 area 120network 10.122.0.0 0.0.255.255 area 0

Eliminates External Routes/LSA Present in Area (Type 5)

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Backbone Area 0

Area 120

Area Border Router

A Totally Stubby AreaABR Forwards

Summary Default to ABR

Totally Stubby AreaUse This for Stable—Scalable Internetworks

Access Config:router ospf 100area 120 stub no-summarynetwork 10.120.0.0 0.0.255.255 area 120

Distribution Configrouter ospf 100area 120 stub no-summarysummary-address 10.120.0.0 255.255.0.0network 10.120.0.0 0.0.255.255 area 120network 10.122.0.0 0.0.255.255 area 0

Minimize the Number of LSA’s and the Need for Any External Area SPF Calculations


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Backbone Area 0

Not So Stubby Area (NSSA)

NSSA ABR Forwards Summary LSAsSummary 0.0.0.0 to ABR

NSSA 120

ABR—Type 7 à Type 5

ASBR Injects LSA Type 7

RIP

Totally Stubby NSSA ABR Forwards

Summary 0.0.0.0 to ABR

Minimize the Number of LSA’s and the Need for Any External Area While Supporting External Connectivity

Access Config:router ospf 100area 120 nssa no-summarynetwork 10.120.0.0 0.0.255.255 area 120

Distribution Configrouter ospf 100area 120 nssa no-summarysummary-address 10.120.0.0 255.255.0.0network 10.120.0.0 0.0.255.255 area 120network 10.122.0.0 0.0.255.255 area 0


SiSiSiSi

SiSiSiSi

Backbone Area 0

Area 120

Area Border Router

ABR’s ForwardSummary 10.120.0.0/16

Summarization Distribution to CoreReduce SPF and LSA Load in Area 0

Access Config:router ospf 100area 120 stub no-summarynetwork 10.120.0.0 0.0.255.255 area 120

Distribution Configrouter ospf 100area 120 stub no-summarysummary-address 10.120.0.0 255.255.0.0network 10.120.0.0 0.0.255.255 area 120network 10.122.0.0 0.0.255.255 area 0

Minimize the Number of LSA’s and the Need for Any SPF Recalculations at the Core


OSPF Default Route to Totally Stubby Area

• Totally stubby area’s are used to isolate the access layer switches from route calculations due to events in other areas

• This means that the ABR (the distribution switch) will send a default route to the access layer switch when the neighbor relationship is established

• The default route is sent regardless of the distribution switches ability to forward traffic on to the core (area 0)

• Traffic could be black holed until connectivity to the core is established

A B

Traffic

Drop

ped U

ntil

Conn

ectivit

y to Co

re

Estab

lished

Defau

lt

Route

SiSi

SiSi

SiSi

SiSi

Note: Solution to this anomaly is being investigated.


SiSi

SiSi

OSPF Timer TuningHigh-Speed Campus Convergence

• OSPF by design has a number of throttling mechanisms to prevent the network from thrashing during periods of instability

• Campus environments are candidates to utilize OSPF timer enhancements

Sub-second hellos

Generic IP (interface) dampening mechanism

Back-off algorithm for LSA generation

Exponential SPF backoff

Configurable packet pacing

Incremental SPF

Reduce SPF Interval

SiSi

SiSi

Reduce Hello Interval


Subsecond Hello’sNeighbor Loss Detection—Physical Link Up

• OSPF hello/dead timers detect neighbor loss in the absence of physical link loss

• Useful in environments where an L2 device separates L3 devices (Layer 2 core designs)

• Aggressive timers are needed to quickly detect neighbor failure

• Interface dampening is required if sub-second hello timers are implemented

Traffic

Drop

ped U

ntil

Neigh

bor L

oss

Detec

tion O

ccurs

OSPF Processing

Failure(Link Up)

A B

SiSi

SiSi

SiSi

SiSi

Access Config:interface GigabitEthernet1/1dampeningip ospf dead-interval minimal hello-multiplier 4

router ospf 100area 120 stub no-summarytimers throttle spf 10 100 5000timers throttle lsa all 10 100 5000timers lsa arrival 80


OSPF LSA Throttling

• By default, there is a 500ms delay before generating router and network LSA’s; the wait is used to collect changes during a convergence event and minimize the number of LSA’s sent

• Propagation of a new instance of the LSA is limited at the originator

timers throttle lsa all

• Acceptance of a new LSAs is limited by the receiver

timers lsa arrival

Traffic Dropped Until

LSA Generated and

Processed

Access Config:interface GigabitEthernet1/1ip ospf dead-interval minimal hello-multiplier 4


A B

SiSi

SiSi

SiSi

SiSi


OSPF SPF Throttling

• OSPF has an SPF throttling timer designed to dampen route recalculation (preserving CPU resources) when a link bounces

• 12.2S OSPF enhancements let us tune this timer to milliseconds; prior to 12.2S one second was the minimum

• After a failure, the router waits forthe SPF timer to expire before recalculating a new route; SPF timer was one second

Traffic

Dropp

ed Un

til

SPF T

imer

Expir

es

Access Config:interface GigabitEthernet1/1ip ospf dead-interval minimal hello-multiplier 4


A B

SiSi

SiSi

SiSi

SiSi


SiSiSiSi

SiSiSiSi

OSPF Routed Access Campus DesignOverview—Fast Convergence

• Detect the event:Decrease the hello-interval and dead-interval to detect soft neighbor failures

Enable interface dampening

Set carrier-delay = 0

• Propagate the event:Summarize routes between areasto limit LSA propagation acrossthe campus

Tune LSA timers to minimize LSA propagation delay

• Process the event:Tune SPF throttles to decrease calculation delays

StubArea120

BackboneArea

0


SiSiSiSi

SiSiSiSi

OSPF Routed Access Campus DesignOverview—Area Design

• Use totally stubby areas to minimize routes in Access switches

• Summarize area routes to backbone Area 0

• These recommendations will reduce number of LSAs and SPF recalculations throughout the network and provide a more robust and scalable network infrastructure

Area Routes Summarized

router ospf 100area 120 stub no-summarysummary-address 10.120.0.0 255.255.0.0network 10.120.0.0 0.0.255.255 area 120network 10.122.0.0 0.0.255.255 area 0

router ospf 100area 120 stub no-summarynetwork 10.120.0.0 0.0.255.255 area 120

Configured asTotally Stubby

Area


SiSiSiSi

SiSiSiSi

OSPF Routed Access Campus DesignOverview—Timer Tuning

• In a hierarchical design, the key tuning parameters are spf throttle and lsa throttle

• Need to understand other LSA tuning in the non-optimal design

• Hello and dead timers are secondary failure detection mechanism

Reduce Hello Interval

Reduce SPF andLSA Interval

router ospf 100area 120 stub no-summaryarea 120 range 10.120.0.0 255.255.0.0timers throttle spf 10 100 5000timers throttle lsa all 10 100 5000timers lsa arrival 80network 10.120.0.0 0.0.255.255 area 120network 10.122.0.0 0.0.255.255 area 0

interface GigabitEthernet5/2ip address 10.120.100.1 255.255.255.254dampeningip ospf dead-interval minimal hello-multiplier 4


Agenda






• Summary


Unicast vs. Multicast

• Expected behavior for Unicast-based applications

• Take advantage of multicast-based applications that provide same service

IP WAN

Headquarters

Branch A

Branch B

UnicastMoH

Multiply Times Number ofUnicast Endpoints

UnicastSoftware

Distribution


Headquarters

Branch A

Branch B

MulticastMoH

Unicast vs. Multicast

One-to-Few Streams Sent toGroup(s) of Receivers

Video/Streaming Media

Multicast Enabled InfrastructureAllows for New Technologies

Less BW Consumed to Provide Same ServiceLess CPU Utilization on Source DevicesLess Overall Impact on Network Devices Replicating and Forwarding Traffic

MulticastSoftware

Distribution

IP WAN


IP Multicast Protocols

• Dense-mode protocolsUses “push” modelFlood and prune behavior

• Sparse-mode protocolsUses “pull” model: traffic sent only to where it is requestedExplicit join behavior

• Enterprise IPmc protocolsPIM, MOSPF, DVMRP,

• PIM—Protocol independent multicastUses underlying Unicast routing protocol to prevent loopsTwo modes: PIM dense mode and PIM sparse mode


Which PIM Mode—Sparse or Dense

“Sparse mode Good! Dense mode Bad!”

Source: “The Caveman’s Guide to IP Multicast”, ©2000, R. Davis


PIM Sparse Mode (RFC 2362)

• Assumes no hosts wants multicast traffic unless they specifically ask for it

• Uses a Rendezvous Point (RP)Senders and receivers “rendezvous” at this point to learn of each others existence

Senders are “registered” with RP by their first-hop router

Receivers are “joined” to the shared tree (rooted at the RP) by their local Designated Router (DR)

• Appropriate for…

Wide scale deployment for both densely and sparsely populated groups in the enterprise

Optimal choice for all production networks regardless of size and membership density


Anycast RP—Overview

• PIM RP deployment optionsStatic, Auto-RP, BSR, and Anycast RP

• Anycast RP provides fast failover and load-balancingMultiple RPs use a single IP address

Two or more routers have same RP address (anycast)

RP address defined as a Loopback Interface

Senders and receivers register/join with closest RP

Closest RP determined from the Unicast routing table

MSDP session(s) run between all RPs

Informs RPs of sources in other parts of network

Facilitates sharing of source information



MSDPMSDP

RecRec RecRec

Src Src

SA SAA

RP1

10.1.1.1B

RP2

10.1.1.1

X



RecRec RecRec

SrcSrc

A

RP1

10.1.1.1B

RP2

10.1.1.1

X


Anycast RP Configuration

ip pim rp-address 10.0.0.1 ip pim rp-address 10.0.0.1

Interface loopback 0ip address 10.0.0.1 255.255.255.255


!ip msdp peer 10.0.0.3 connect-source loopback 1ip msdp originator-id loopback 1



!ip msdp peer 10.0.0.2 connect-source loopback 1ip msdp originator-id loopback 1

MSDPMSDPB

RP2

A

RP1

C D


PIM Design Rules for Routed Campus

• Use PIM sparse mode• Enable PIM sparse mode on

ALL access, distribution and core layer switches

• Enable PIM on ALL interfaces• Use Anycast RPs in the core for

RP redundancy and fast convergence

• IGMP-snooping is enabled when PIM is enabled on a VLAN interface (SVI)

• (Optional) force the multicast traffic to remain on the shared-tree to reduce (S, G) state

• (Optional) use garbage canRP to black-hole unassigned IPmc traffic

IPmc Sources

WAN Internet


SiSiSiSi

SiSiSiSi SiSi SiSiSiSiSiSi

IP/TV ServerCall Managerw/MoH

RP-Left10.122.100.1

RP-Right10.122.100.1


Multicast Routed Access Campus DesignThings You Don’t Have to Do…

• Tune PIM query interval for designated router convergence

• Configure designated router to matchHSRP primary

• Configure PIM snooping on L2 switchesbetween L3 switches

• Worry about all those L2/L3 flowinconsistency issues


Agenda






• Summary


Routing to the Edge Advantages? Yes, with a Good Design

• Sub-200 msec convergence for EIGRP and OSPF• Ease of implementation; fewer things to get right• Troubleshooting; well known protocols and tools• Simplified IP Multicast deployment• Considerations; spanning VLANs, IP addressing, IGP selection

A B

SiSiSiSi

SiSiSiSi

00.2

0.40.60.8

11.21.41.61.8

2

RPVST+ OSPF EIGRP

UpstreamDownstream

Sec

onds


Routed Access DesignSummary

• EIGRP or OSPF routed links between access and distribution• Routed interfaces, not VLAN trunks, between switches• Equal cost multi path to load balance traffic across network• Route summarization at distribution with stub routers/areas

• Single (IGP) control plan to configure/manage/troubleshoot

10.1.20.010.1.120.0


EIGRP or OSPFEqual Cost Multi Path

Layer 2

Layer 3

SiSiSiSi

SiSiSiSi


10.1.40.010.1.140.0

Access

Distribution


Recommended Reading

• Continue your Networkerslearning experience with further reading for this session from Cisco Press

• Check the Recommended Reading flyer for suggested books

Available Onsite at the Cisco Company Store


EIGRPCore Layer Configuration

!

router eigrp 100

network 10.0.0.0

no auto-summary

interface TenGigabitEthernet3/1

description 10GigE to Distribution 1

ip address 10.122.0.29 255.255.255.252

ip pim sparse-mode

ip hello-interval eigrp 100 1

ip hold-time eigrp 100

ip authentication mode eigrp 100 md5

ip authentication key-chain eigrp 100 eigrp

carrier-delay msec 0

mls qos trust dscp

!

interface TenGigabitEthernet3/2

description 10GigE to Distribution 2

ip address 10.122.0.37 255.255.255.252

ip pim sparse-mode

ip authentication mode eigrp 100 md5

ip authentication key-chain eigrp 100 eigrp

carrier-delay msec 0

mls qos trust dscp

6k-core configuration


EIGRPDistribution Layer Configuration

interface TenGigabitEthernet4/2description 10 GigE to Core neighborip address 10.122.0.38 255.255.255.252ip pim sparse-modeip authentication mode eigrp 100 md5ip authentication key-chain eigrp 100 eigrpip summary-address eigrp 100 10.120.0.0

255.255.0.0 5mls qos trust dscp

!

router eigrp 100network 10.0.0.0distribute-list Default out GigabitEthernet3/1distribute-list Default out GigabitEthernet3/2 …distribute-list Default out

GigabitEthernet9/15no auto-summary

!

ip access-list standard Defaultpermit 0.0.0.0permit 10.0.0.0

interface GigabitEthernet3/2description typical link to Access neighborip address 10.120.0.50 255.255.255.252ip pim sparse-modeip hello-interval eigrp 100 1ip hold-time eigrp 100 3ip authentication mode eigrp 100 md5ip authentication key-chain eigrp 100 eigrpcarrier-delay msec 0mls qos trust dscp

!

interface TenGigabitEthernet4/3description 10GigE to Distribution neighborip address 10.120.0.22 255.255.255.252ip pim sparse-modeip hello-interval eigrp 100 1ip hold-time eigrp 100 3ip authentication mode eigrp 100 md5ip authentication key-chain eigrp 100 eigrpmls qos trust dscp

6k-distribution configuration


EIGRPAccess Layer Configuration

interface Vlan4ip address 10.120.4.1 255.255.255.0ip helper-address 10.121.0.5no ip redirectsip pim sparse-modeip igmp snooping fast-leave

!interface Vlan104ip address 10.120.104.1 255.255.255.0ip helper-address 10.121.0.5no ip redirectsip pim sparse-modeip igmp snooping fast-leave

!router eigrp 100passive-interface defaultno passive-interface GigabitEthernet1/1no passive-interface GigabitEthernet2/1network 10.0.0.0no auto-summaryeigrp stub connected

interface GigabitEthernet2/1description cr3-6500-2 Distributionno switchportip address 10.120.0.53 255.255.255.252ip hello-interval eigrp 100 1ip hold-time eigrp 100 3ip authentication mode eigrp 100 md5ip authentication key-chain eigrp 100 eigrpip pim sparse-modecarrier-delay msec 0qos trust dscptx-queue 3

priority high

!

interface FastEthernet3/5description Host port w/ IP Phoneswitchport access vlan 4switchport mode accessswitchport voice vlan 104qos trust costx-queue 3

priority highspanning-tree portfastspanning-tree bpduguard enable

Catalyst 4507 configuration


OSPFCore Layer Configuration

router ospf 100router-id 10.122.10.2log-adjacency-changestimers throttle spf 10 100 5000timers throttle lsa all 10 100 5000timers lsa arrival 80passive-interface Loopback0passive-interface Loopback1passive-interface Loopback2network 10.122.0.0 0.0.255.255 area 0.0.0.0

!

interface Port-channel1description Channel to Peer Core nodedampeningip address 10.122.0.19 255.255.255.254ip pim sparse-modeip ospf dead-interval minimal hello-multip 4load-interval 30carrier-delay msec 0mls qos trust dscp

!

interface TenGigabitEthernet3/1description 10GigE to Distribution 1dampeningip address 10.122.0.20 255.255.255.254ip pim sparse-mode ip ospf dead-interval minimal hello-multip 4load-interval 30carrier-delay msec 0mls qos trust dscp

!

6k-core configuration


OSPFDistribution Layer Configuration

router ospf 100router-id 10.122.102.1log-adjacency-changesarea 120 stub no-summaryarea 120 range 10.120.0.0 255.255.0.0timers throttle spf 10 100 5000 timers throttle lsa all 10 100 5000timers lsa arrival 80network 10.120.0.0 0.0.255.255 area 120network 10.122.0.0 0.0.255.255 area 0

interface GigabitEthernet3/2description 3750 Access Switchdampeningip address 10.120.0.8 255.255.255.254ip pim sparse-modeip ospf dead-interval minimal hello-multip 4load-interval 30carrier-delay msec 0mls qos trust dscp

!

interface TenGigabitEthernet4/1description 10 GigE to Core 1dampeningip address 10.122.0.26 255.255.255.254ip pim sparse-modeip ospf dead-interval minimal hello-multip 4load-interval 30carrier-delay msec 0mls qos trust dscp

6k-dist-left configuration


OSPFAccess Layer Configuration

interface Vlan2description Data VLAN for 3750 Dataip address 10.120.2.1 255.255.255.0ip helper-address 10.121.0.5no ip redirectsip pim sparse-modeip igmp snooping fast-leave

!

interface Vlan102description Voice VLAN for 3750-accessip address 10.120.102.1 255.255.255.0ip helper-address 10.121.0.5no ip redirectsip pim sparse-modeip igmp snooping fast-leave

!

router ospf 100router-id 10.120.250.2log-adjacency-changesarea 120 stub no-summarytimers throttle spf 10 100 5000timers throttle lsa all 10 100 5000timers lsa arrival 80passive-interface defaultno passive-interface GigabitEthernet1/0/1no passive-interface GigabitEthernet3/0/1network 10.120.0.0 0.0.255.255 area 120

interface GigabitEthernet1/0/1description Uplink to Distribution 1no switchportdampeningip address 10.120.0.9 255.255.255.254ip pim sparse-modeip ospf dead-interval minimal hello-multip 4load-interval 30carrier-delay msec 0srr-queue bandwidth share 10 10 60 20srr-queue bandwidth shape 10 0 0 0 mls qos trust dscpauto qos voip trust

interface FastEthernet2/0/1description Host port with IP Phoneswitchport access vlan 2switchport voice vlan 102srr-queue bandwidth share 10 10 60 20srr-queue bandwidth shape 10 0 0 0 mls qos trust device cisco-phonemls qos trust cosauto qos voip cisco-phone spanning-tree portfastspanning-tree bpduguard enable

3750-Access configuration


PIMDistribution and Access Layer

ip multicast-routingip igmp snooping vlan 4 immediate-leave ip igmp snooping vlan 104 immediate-leave no ip igmp snooping ! interface VlanX

ip address 10.120.X.1 255.255.255.0 ip helper-address 10.121.0.5 no ip redirects ip pim sparse-mode

!ip pim rp-address 10.122.100.1 GOOD-IPMC

overrideip pim spt-threshold infinity!ip access-list standard Default

permit 10.0.0.0ip access-list standard GOOD-IPMC

permit 224.0.1.39permit 224.0.1.40permit 239.192.240.0 0.0.3.255permit 239.192.248.0 0.0.3.255

ip multicast-routing!interface Loopback2

description Garbage-CAN RPip address 2.2.2.2 255.255.255.255

!interface Y

description GigE to Access/Core ip address 10.122.0.Y 255.255.255.252 ip pim sparse-mode

!!ip pim rp-address 10.122.100.1 GOOD-IPMC

overrideip pim rp-address 2.2.2.2ip pim spt-threshold infinity!ip access-list standard Default

permit 10.0.0.0ip access-list standard GOOD-IPMC

permit 224.0.1.39permit 224.0.1.40permit 239.192.240.0 0.0.3.255permit 239.192.248.0 0.0.3.255

4507k-access configuration6k-dist-left configuration


PIMCore Layer RP Configuration—1

ip multicast-routing!interface Loopback0description MSDP PEER INT ip address 10.122.10.2 255.255.255.255

! interface Loopback1 description ANYCAST RP ADDRESS ip address 10.122.100.1 255.255.255.255

! interface Loopback2 description Garbage-CAN RP ip address 2.2.2.2 255.255.255.255

! interface TenGigabitEthernet M/Zip address 10.122.0.X 255.255.255.252ip pim sparse-mode

!ip pim rp-address 2.2.2.2 ip pim rp-address 10.122.100.1 GOOD-IPMC

override ip pim accept-register list PERMIT-SOURCES ip msdp peer 10.122.10.1 connect-source

Loopback0 ip msdp description 10.122.10.1

ANYCAST-PEER-6k-core-leftip msdp originator-id Loopback0

ip multicast-routing!interface Loopback0description MSDP PEER INT ip address 10.122.10.1 255.255.255.255

! interface Loopback1 description ANYCAST RP ADDRESS ip address 10.122.100.1 255.255.255.255

! interface Loopback2 description Garbage-CAN RP ip address 2.2.2.2 255.255.255.255

! interface TenGigabitEthernet M/Y ip address 10.122.0.X 255.255.255.252ip pim sparse-mode

!ip pim rp-address 2.2.2.2 ip pim rp-address 10.122.100.1 GOOD-IPMC

override ip pim accept-register list PERMIT-SOURCES ip msdp peer 10.122.10.2 connect-source

Loopback0 ip msdp description 10.122.10.2

ANYCAST-PEER-6k-core-right ip msdp originator-id Loopback0

6k-core Right Anycast-RP configuration6k-core Left Anycast-RP configuration


PIMCore Layer RP Configuration—2

! Continued from previous slide! ip access-list standard GOOD-IPMCpermit 224.0.1.39permit 224.0.1.40permit 239.192.240.0 0.0.3.255permit 239.192.248.0 0.0.3.255

!ip access-list extended PERMIT-SOURCESpermit ip 10.121.0.0 0.0.255.255

239.192.240.0 0.0.3.255 permit ip 10.121.0.0 0.0.255.255

239.192.248.0 0.0.3.255

! Continued from previous slide! ip access-list standard GOOD-IPMCpermit 224.0.1.39permit 224.0.1.40permit 239.192.240.0 0.0.3.255permit 239.192.248.0 0.0.3.255

!ip access-list extended PERMIT-SOURCESpermit ip 10.121.0.0 0.0.255.255

239.192.240.0 0.0.3.255 permit ip 10.121.0.0 0.0.255.255

239.192.248.0 0.0.3.255

6k-core Right Anycast-RP configuration6k-core Left Anycast-RP configuration

deploying a fully routed enterprise campus network€¦ · • eigrp/ospf routing preference over...

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